Condenser assemblies for heating, ventilating, air conditioning, and refrigeration systems

ABSTRACT

Embodiments of a modular condenser unit are provided. The modular condenser unit may include a housing and a first condenser coil and a second condenser coil disposed within a volume of the housing. A fan may also be disposed in an end of the housing and adapted to draw air through at least one of the first condenser coil and the second condenser coil. In some embodiments, the first condenser coil and/or the second condenser coil may be micro-channel condenser coils.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional patent application of U.S.Provisional Patent Application No. 61/262,763 entitled “Use ofMicro-Channel Condenser Technology in The Refrigeration System forGround Support Equipment Used on Commercial Aircraft”, filed Nov. 19,2009, which is herein incorporated by reference.

BACKGROUND

The invention relates generally to heating, ventilation, airconditioning, and refrigeration (HVACR) systems, and, more particularly,to modular HVACR systems.

HVACR systems are utilized for a variety of applications that requirethe temperature and quality of surrounding air to be regulated. Forexample, HVACR systems are utilized to provide ventilation, to filterair, and to maintain desirable pressure relationships for buildings,aircraft, and so forth. For further example, HVACR systems may beprovided on a ground support equipment cart to serve aircraft parked atgates. As such, HVACR systems typically include a refrigeration cyclethat includes various heat exchangers that cooperatively function tooutput the desired air stream. Such heat exchangers are typicallyprovided as integral components of the HVACR unit.

Unfortunately, in many traditional systems, if a single internalcomponent, such as a condenser, malfunctions, the entire HVACR systemmust be shut down until the malfunction is fixed or a broken part isreplaced. In some industries, such a situation may result in lostproductivity due to the resulting downtime. Additionally, traditionalcondensers provided as integral parts of the HVACR system typicallyutilize copper tubes with aluminum fins or aluminum tubes with spinyfins in the condenser coil design. Such condenser coil designs areheavy, require large amounts of refrigerant for proper operation, andmay have corrosion issues due to dissimilar metals. Accordingly, thereexists a need for improved HVACR systems that overcome such drawbacksassociated with traditional systems including typical condensertechnology.

BRIEF DESCRIPTION

In an exemplary embodiment, a condenser assembly includes a housingdefining an airflow volume, a divider separating the airflow volume intoa first volume and a second volume, a first condenser coil disposed in aside of the housing adjacent to the first volume, and a second condensercoil disposed in a side of the housing adjacent to the second volume.The condenser assembly also includes a first fan disposed in a first endof the housing to draw air through the first condenser coil and thefirst volume and a second fan disposed in a second end opposite thefirst end of the housing to inject air into the second volume andthrough the second condenser coil.

In another embodiment, a modular condenser unit includes a housing, afirst micro-channel condenser coil disposed within a volume of thehousing, a second micro-channel condenser coil disposed within thevolume of the housing, and a fan disposed in an end of the housing andconfigured to draw air through at least one of the first micro-channelcondenser coil and the second micro-channel condenser coil.

In another embodiment, a method of assembling a condenser moduleincludes providing a housing defining an airflow volume, providing adivider adapted to separate the airflow volume into a first volume and asecond volume, disposing a first condenser coil in a first side of thehousing adjacent to the first volume, and disposing a second condensercoil in a second side of the housing adjacent to the second volume. Themethod also includes providing a first fan in a first end of the housingbeing configured to draw air through the first condenser coil and thefirst volume, and providing a second fan in a second end opposite thefirst end of the housing being configured to inject air into the secondvolume and through the second condenser coil.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an exemplary modular air conditioning(AC) unit that is configurable to output any of a range of conditioningcapacities;

FIG. 2 illustrates an exemplary assembly process for a modular AC unitin accordance with aspects of the present invention;

FIG. 3 illustrates an exemplary method of assembling the modular AC unitof FIGS. 1 and 2 to meet the desired output air conditioning capacity;

FIG. 4 is a block diagram illustrating the configurability of themodular AC unit from a group of blowers, a group of evaporators, and agroup of condensers in accordance with aspects of the present invention;

FIG. 5 is a perspective view of an exemplary condenser module inaccordance with embodiments of the present invention;

FIG. 6 is a cross-section of the exemplary condenser module taken alongline 6-6 of FIG. 5;

FIG. 7 is an exploded section of the exemplary condenser module of FIG.6 in accordance with aspects of the present invention;

FIG. 8 illustrates a side view of a section of an exemplary dividerlocated in the exemplary condenser module of FIG. 5;

FIG. 9 illustrates exemplary control logic that may be implemented toutilize one or more of a variety of sensors located in the modular ACunit to determine an appropriate operating mode;

FIG. 10 illustrates exemplary operating logic that may be employed by anexemplary controller to operate the modular AC unit in vent mode;

FIG. 11 illustrates an exemplary basic startup control logic sequencethat may be implemented for a modular AC system to determine control ofthe modular unit in accordance with aspects of the present invention;

FIG. 12 illustrates exemplary logic for operating the modular AC unit incooling mode;

FIG. 13 illustrates an exemplary method for calculating a number ofnecessary compressor stages during the cooling mode startup inaccordance with aspects of the present invention;

FIG. 14 illustrates an exemplary method that may be utilized by anexemplary controller to control operation of one or more condenser fansin the modular AC unit;

FIG. 15 illustrates an exemplary method that may be employed to optimizecooling capacity of the modular AC unit in accordance with aspects ofthe present invention;

FIG. 16 illustrates an exemplary critical fault alerting method inaccordance with aspects of the present invention; and

FIG. 17 illustrates an exemplary non-critical fault alerting method inaccordance with aspects of the present invention.

DETAILED DESCRIPTION

As described in detail below, embodiments of a modular HVACR system areprovided. The modular system may include one or more substantiallyidentical condenser and evaporator modules that are adapted to becoupled together with an appropriate blower module and base unit tocooperatively function to generate a desired output air capacity, asdesired by an operator. As such, presently contemplated embodiments ofthe evaporator, condenser, and blower modules may be adapted to functiontogether in a variety of system configurations. Further, the condensermodules may be adapted to facilitate proper airflow through thecondenser module when operating as part of the modular system. As such,embodiments of the condenser module may include micro-channelcondensers, dividers, fans, and so forth, appropriately coupled togetherto establish the desired airflow paths.

The modularity of the disclosed systems offers advantages overtraditional non-modular systems. For example, the modularity of thedisclosed systems may allow for increased system efficiency andresponsiveness as well as decreased system downtime as compared totraditional non-modular systems. Such modularity may be based upon useof self-similar evaporator and condenser modules that can be associatedwith one another in various combinations. The combinations may provideredundancy, accommodate temporary or longer-term changing capacity needs(lower or higher), and may allow for field-changeable configurations,such as to interchangeably provide a lower output air capacity or ahigher output air capacity depending upon the application needs. Theresulting systems may be used in a wide range of applications, but areparticularly well suited to temporarily supplying conditioned air toaircraft and other non-permanent installations. While the modularsystems described below are not presented as specifically includingtheir own dedicated power sources, they may draw power from the powergrid, when available, but may also be provided with power fromgenerators (e.g., engine-driven equipment) and other power sources.

It should be noted that the modular air conditioning units describedherein may be designed to deliver any of a variety of types ofconditioned air, such as air which has been cooled, filtered, and/orotherwise conditioned (e.g., heated). As such, the modular AC unit maybe configured to cool incoming air, heat incoming air or otherwisecondition the incoming air. Accordingly, as used herein, the term“conditioned air” is not meant to be construed only as cooled air, butrather is meant to refer to air conditioned in any of a variety ofsuitable ways Likewise, the term “conditioning unit” is not meant tolimit embodiments of the invention to units that cool air, but rather ismeant to encompass units that condition air in a variety of suitableways.

Turning now to the drawings, FIG. 1 is a perspective view of a modularair conditioning (AC) unit 10 that is configurable to output any of arange of conditioning capacities. For example, the module AC unit 10 maybe configurable for a 30 ton refrigeration capacity, a 60 tonrefrigeration capacity, a 90 ton refrigeration capacity, a 120 tonrefrigeration capacity, or any other suitable air conditioning capacity.As such, in the illustrated embodiment, the modular AC unit 10 includesa blower module 12 including louvers 14 and an internal controller 15, acondenser module 16, and an evaporator module 18 including louvers 20.The condenser module 16 includes a first fan 22, a second fan 24, andlouvers 26, although additional fans may also be provided, for example,a third fan and a fourth fan located on a back side of the condensermodule 16. A hose connection 28, which may couple the modular AC unit 10to a downstream device (e.g., an aircraft), is coupled to the evaporatormodule 18 in the illustrated embodiment, but may be located in anysuitable location on the modular AC unit 10 in other embodiments.

During operation, the modular AC unit 10 is adapted to receive incomingair, condition such air, and output the conditioned air for use in adesired downstream application. For example, in one embodiment, themodular AC unit 10 may be located on a ground support equipment cart foran aircraft and, accordingly, may output the conditioned air to anassociated aircraft via connection 28. As such, the modular AC unit 10may be adapted to function as a refrigeration circuit, thus receivingambient air and outputting cooled air. To that end, during use, theblower unit 12 receives and circulates incoming air. The condensermodule 16 and the evaporator module 18 cooperate to function as a heatexchanger module. For example, the blower module 12, the condensermodule 16, and the evaporator module 18 function in a refrigerationcycle, which utilizes a vapor-compression cycle to generate conditionedair. In such embodiments, the condenser module 16 receives a refrigerantand subsequently removes heat from the refrigerant by condensing thevaporized refrigerant into a liquid. Additionally, the evaporator module18 vaporizes a received refrigerant, absorbing heat due to the latentheat of vaporization and cooling the ambient air moved over theevaporator coils by the blower.

The embodiment illustrated in FIG. 1 includes one blower module 12, onecondenser module 16, and one evaporator module 18. However, as shown inFIG. 2, the modular AC unit 10 may include any number of substantiallyidentical condenser modules 16 and any number of substantially identicalevaporator modules 18. Specifically, FIG. 2 illustrates a base unit 30that is adapted to receive the appropriate number of components toachieve the desired output air capacity. For example, in the illustratedembodiment, the base unit 30 is adapted to receive the blower module 12,as indicated by arrow 32. The substantially identical condenser modules16 are adapted to be received by the substantially identical evaporatormodules 18, as indicated by arrows 34, and the base unit 30 isconfigured to receive the substantially identical evaporator modules 18,as indicated by arrows 36.

As indicated in FIG. 2, any number of substantially identical condensermodules 16 and any number of substantially identical evaporator modules18 may be mounted to the base unit 30 to achieve the desired output.That is, embodiments of the present invention facilitate formation of amodular AC unit with any of a variety of suitable output capacities byallowing an operator to couple an appropriate blower module with asuitable number of evaporator modules and condenser modules. Forinstance, the user may couple additional condenser modules andadditional evaporator modules to the base unit to increase the outputcapacity of the modular AC unit until the maximum capacity of the blowermodule has been reached. Subsequently, if an even greater outputcapacity is desired, the user may replace the blower module with anotherblower module of increased capacity and add additional condenser andevaporator modules as desired. Still further, in some embodiments, theevaporator unit and the condenser unit may be provided as a singlemodular assembly. That is, in certain embodiments, a modular heatexchanger module may be provided. In such embodiments, the modular heatexchanger module may be configured to function both as an evaporator andas a condenser.

It should be noted that embodiments of the present invention may includemultiple base units 30 from which an operator may choose the appropriatebase size for the given application. For example, each base unit may beadapted to receive a predetermined number of condenser and evaporatormodules and, thus, may have an associated maximum output capacity. If anincrease in the desired output capacity beyond the maximum outputcapacity supported by the chosen base unit is desired, a new base unitmay be chosen to accommodate the additional condenser and evaporatormodules. Furthermore, it should also be noted that the base unit 30 ofFIG. 2 is exemplary, and a variety of advantageous modifications may bemade to such a unit during implementation. For example, the base unit 30may include wheels that impart the modular AC unit with mobility. Forfurther example, the base unit 30 may be configured for use in a standmounted, bridge mounted, towable, or truck/heavy vehicle mountedconfigurations.

The modularity of the modular AC unit 10 offers distinct advantages overnon-modular systems. For example, while non-modular systems may limitthe operator to a fixed maximum output capacity, presently disclosedmodular AC systems are configurable for a variety of output capacitiessince additional modules may be added as needed. For further example,since each modular unit is substantially identical, the modularity ofthe system may allow for easy replacement or repair of malfunctioningmodules. If a malfunction is identified in a module, the module may bereplaced with a substantially identical module of the same type whilethe original module is repaired. As such, the modular AC systemsdisclosed herein may allow for repair of malfunctions without the needfor system downtime.

In the embodiments illustrated in FIGS. 1 and 2, the blower module 12 isshown mounted to a left side portion of the base unit 30, and thecondenser modules 16 are shown mounted on top of the evaporator modules18. However, it should be noted that in other embodiments, differentconfigurations of the modular AC unit 10 may be realized in which suchcomponents are coupled together in various other ways. For example, inone embodiment, the blower may be located beneath the condenser modulesand the evaporator modules, and the base unit 30 may be configured todirectly contact only the blower module. Such an embodiment may beadvantageous in applications involving space constraints. Indeed, itshould be noted that any suitable arrangement of the various modules onany appropriate base unit may be employed in further embodiments.

FIG. 3 illustrates a method 38 of assembling the modular AC unit 10 ofFIGS. 1 and 2 to meet the desired output air conditioning capacity. Themethod 38 includes the step of selecting a base unit (block 40). Asbefore, the base unit may be adapted for placement directly on a floor,on a set of wheels, attached to a bridge (e.g., adjacent to anaircraft), or any other suitable location. The method 38 also includesselecting a blower from a group of blowers of different outputcapacities (block 42) and mounting the selected blower to the base unit(block 44). The method also includes selecting a desired number ofsubstantially identical modular evaporator units (block 46) and mountingthe selected evaporator units to the base unit (block 48). The methodfurther includes selecting a desired number of substantially identicalmodular condenser units (block 50) and mounting the selected condenserunits to the base unit (block 52). It should be noted that in someembodiments, the evaporator units and/or the condenser units may not bemounted directly to the base unit, but rather such units may beindirectly coupled to the base unit.

The method also includes the step of adding and/or replacing modules onthe base unit as needed based on the desired output capacity of themodular AC unit (block 54). That is, after the modular AC unit has beenoriginally configured, the unit may be reconfigured to provide adifferent output capacity. As before, the modularity of the assembledsystem offers advantages over existing non-modular systems. For example,before coupling to the base unit, each modular unit may be independentlyassembled and tested, thereby simplifying the troubleshooting process ifa malfunction occurs. For further example, since the modular AC units ofdifferent capacities have substantially the same maintenance,operational, and service training, an operator of one modular AC unitneed not undergo additional training to use and/or service anothermodular AC unit.

FIG. 4 is a block diagram 56 further illustrating the configurability ofthe modular AC unit 10. The diagram 56 includes a group of blower units58, a group of evaporator units 60, a group of condenser units 62, afirst modular AC unit 64, a second modular AC unit 66, and a thirdmodular AC unit 68. As shown, the group of blower units 58 includes afirst blower 70 of a low cooling capacity, a second blower 72 of amedium cooling capacity, and a third blower 74 of a high coolingcapacity. The group of evaporator units 60 includes three substantiallysimilar evaporator modules 18, and the group of condenser units 62includes three substantially identical condenser modules 16. However, itshould be noted that additional blower modules, evaporator modules, andcondenser modules may be provided in further embodiments.

As illustrated, a variety of modular AC units may be formed by couplingcomponents of the blower group 58, the evaporator group 60 and thecondenser group 62 in an appropriate manner. For example, in oneembodiment, an operator may choose the first blower 70, a singleevaporator module 18 and a single condenser module 16, as shown in thefirst modular AC unit 64. In such an embodiment, the evaporator module18 and the condenser module 16 may collectively function as a 30 tonheat exchanger module and, accordingly, the first modular AC unit 64 maybe a 30 ton nominal AC unit. For further example, in another embodiment,an operator may choose the second blower 72, two evaporator modules 18,and two condenser modules 16, as shown in the second modular AC unit 66.In such an embodiment, the evaporator modules 18 and the condensermodules 16 may collectively function as a 60 ton heat exchanger moduleand, accordingly, the second modular AC unit 66 may be a 60 ton nominalAC unit. Similarly, in a further embodiment, the user may choose thethird blower 74, three evaporator modules 18, and three condensermodules 16 and, accordingly, the third modular AC unit 68 may beconfigured to function as a 90 ton nominal AC unit.

It should be noted that the blower module chosen by the user may bechosen based on the maximum desired output capacity. That is, forexample, the user may choose the medium cooling capacity blower 72 butmay initially only choose a single evaporator module 18 and a singlecondenser module 16. Such a choice may allow the operator to utilize thesame blower module and base unit while adding additional evaporator andcondenser units as the desired output capacity increases. Indeed, thesystem illustrated in FIG. 4 may allow the user to configure anappropriate modular AC unit as dictated by the anticipated or actualdownstream output demand.

FIG. 5 is a perspective view of an exemplary condenser module 16 inaccordance with embodiments of the present invention. The foregoingcondenser module 16 may include a variety of features that offerdistinct advantages over traditional condensers designed for use innon-modular systems. For example, in some embodiments, the condensermodule 16 may utilize micro-channel condenser coil technology in thecondensing circuit of the condenser module 16. In such an embodiment,the micro-channel condenser components may be smaller and lighter thantraditional technology (e.g., copper tubes with aluminum fins, aluminumtubes with fins, etc.), thus reducing the weight of the modular AC unitas compared to existing non-modular systems. Additionally, in someembodiments, the micro-channel condenser technology may use lessrefrigerant than traditional systems, thereby further reducing the sizeand weight of the unit and increasing unit efficiency. Still further,micro-channel condenser coils may be more resistant to damage andcorrosion than traditional fin systems.

The illustrated condenser module 16 includes four fans: two front fans22 and 24 and two back fans (not shown in FIG. 5). In some embodiments,as described in more detail below, the four fans may be independentlycontrolled, for example, by controller 15. The foregoing feature mayoffer advantages over traditional systems since such control may enableeach of the fans to be operated independent of the operation of theother fans. For example, in cold environments in which only a limitednumber of fans are necessary, the excessive fans may be turned OFF.Still further, in such embodiments, the number of activated fans may bedetermined based on a measured or calculated refrigerant head pressure.

FIGS. 6 and 7 illustrate exemplary internal components of embodiments ofthe novel condenser modules 16 disclosed herein. Specifically, FIG. 6 isa section of an exemplary condenser module 16 utilizing micro-channelcondenser coils taken along line 6-6 of FIG. 5. FIG. 7 illustrates anexploded section of the exemplary condenser module 16 shown in FIG. 6.As shown in the foregoing illustrations, the condenser module 16includes the input fan 22 with a motor 76, a top condenser coil 78,louvers 26, a bottom condenser coil 80, a bottom panel 82 with a firstgrid portion 84 and a second grid portion 86, a divider 88, an outputfan 90 with motor 92, and a side panel 93. In the illustratedembodiments, the top condenser coil 78 and the bottom condenser coil 80are parallel to each other. However, in other embodiments, the condensercoils 78 and 80 may be positioned in any other suitable arrangement withrespect to one another.

During operation, the input fan 22 establishes a first airflow path, asdefined by arrows 94, 96, 98, and 100 through a first chamber 102 of thecondenser module 16. As shown, the fan 22 draws air into the firstchamber 102, as shown by arrow 94, through the first chamber 102 and thetop condenser coil 78, as shown by arrow 96, and through the louvers 26into the surrounding environment, as shown by arrows 98 and 100. Assuch, a first volume of the condenser module 16 is established betweenthe divider 88 and the top condenser coil 78, and the first airflow pathis established through the first volume.

Similarly, the output fan 90 establishes a second airflow path through asecond chamber 104 of the condenser module 16, as indicated by arrows106, 108, 110, 112, and 114. Specifically, air is drawn through thegrids 84 and 86 of the bottom panel 82, as indicated by arrows 106 and108, and through the second chamber 104, as indicated by arrow 110. Theair is further circulated to the surrounding environment via openings ina covering over fan 92, as indicated by arrows 112 and 114. As such, asecond volume of the condenser module 16 is established between thedivider 88 and the bottom condenser coil 80, and the second airflow pathis established through the second volume.

It should be noted that in some embodiments, the air drawn in throughbottom panel 82, indicated by arrows 106 and 108, may be received fromthe evaporator module 18. In such embodiments, the air 106 and 108,after drawn through the bottom condenser coil 80 into chamber 104, maybe substantially hotter than air in chamber 102. Accordingly, the bottomcondenser coil 80 may be associated with the grids 84 and 86, whichcooperate to approximately evenly distribute the incoming air 106 and108 across the bottom condenser coil 80. Further, in such embodiments,the divider 88 may split the volume of the condenser module 16 into thefirst chamber 102 and the second chamber 104 and may substantiallythermally isolate such chambers. That is, the divider 88, in someembodiments, may substantially reduce or prevent the hot air 106, 108,and 110 entering the second chamber 104 from heating up the cooler air,94 and 96, entering the first chamber 102.

FIG. 8 illustrates a side view of a section of an exemplary divider 88showing one possible mechanism for maintaining separate air temperaturesin the first chamber 102 and the second chamber 104. In the illustratedembodiment, the divider 88 includes a first plate 116, a second plate118, and an insulating medium 120 disposed therebetween. Duringoperation, the insulating medium 120 may facilitate the substantiallythermal isolation of the first chamber 102 from the second chamber 104.For example, in embodiments in which the air 110 is substantially warmerthan the air 96, the temperature of the air 96 may be substantiallyunaffected by the warmth of air 110. It should be noted that theinsulating medium 120 may be any appropriate fluid, gel, solid, and soforth. For instance, in one embodiment, the insulating medium 120 may beair.

FIGS. 9-17 illustrate exemplary logic that may be employed by acontroller or processor associated with the modular AC units disclosedherein. It should be noted that the controller and/or processor may belocated in any suitable location in or on the modular AC unit. Forexample, in one embodiment, the controller or processor may be locatedin the blower module, as shown in FIG. 1. In such embodiments, thecontroller or processor may be communicatively coupled to the condenserand/or evaporator modules which may include receiving circuitryconfigured to receive control commands from the main controller orprocessor and to implement such commands in the condenser or evaporatormodule.

Specifically, FIG. 9 illustrates control logic 130 that may beimplemented to utilize one or more of a variety of sensors located inthe modular AC unit to determine an appropriate operating mode. Based onone or more inputs received from such probes, the controller may controlthe mode and operation of the modular AC unit even when one or moreprobes fail, as described in detail below. When the modular AC unit isin auto mode, the controller may first inquire as to whether cabin probefeedback is detected (block 132). If the cabin probe is present, thecontroller inquires whether the cabin temperature is above a firstthreshold (block 134), and if the temperature does exceed the firstthreshold, cool mode may be activated (block 136). For example, in oneembodiment, the first threshold may be equal to approximately 73° F.,and if the cabin temperature exceeds this value, the modular AC unitenters cool mode to reduce the cabin temperature.

If the cabin temperature is not above the first threshold, thecontroller inquires whether the cabin temperature is between a secondthreshold and the first threshold (block 138), and if the temperature iswithin this range, vent mode is activated (block 140). For example, thesecond threshold may be approximately 65° F., and if the cabintemperature is between 65° F. and 73° F., vent mode is activated tomaintain the temperature in this range. If the temperature is outsidethis range, the controller may inquire if the cabin temperature is belowthe second threshold (block 142), and if so, heat mode is activated(block 144) to bring the cabin temperature back within the desiredrange. As such, if the cabin temperature probe is functioning, the cabintemperature feedback may be utilized by the controller to determine anappropriate mode of operation.

If the cabin temperature probe malfunctions and cabin probe feedback isnot available, the controller inquires as to whether ambient probefeedback is available (block 146), and if so, the controller inquires asto whether the ambient temperature exceeds a third threshold (e.g., 45°F.) value (block 148). If so, cool mode is activated (block 136). If thethird threshold is not exceeded, the controller checks whether theambient temperature is between a fourth threshold (e.g., 35° F.) and thethird threshold (e.g., 45° F.) value (block 150). If so, vent mode isactivated (block 140) to maintain the ambient temperature in the desiredrange. If the ambient temperature is not within the desired range, thecontroller checks whether the ambient temperature is below the fourththreshold (block 152) and if so, heat mode is activated (block 144) tobring the ambient temperature back in the desired range.

If feedback is not available from the ambient temperature probe (e.g.,the ambient temperature probe has malfunctioned), the controller checksfor feedback from the discharge probe (block 154). If the dischargeprobe feedback is available, the controller selects an appropriate modebased on the detected discharge air temperature and one or more desiredset points (block 156), as before. If feedback is not available from thedischarge temperature probe, the controller directs the modular AC unitto shut down (block 158). As such, the controller may utilize any one ofa variety of feedback probes to determine the appropriate operating modefor the modular AC unit. Accordingly, embodiments of the presentinvention may allow for sensor failure without the need for unitshutdown since the controller may use any of a variety of suitableprobes to direct control of the modular unit.

FIG. 10 illustrates exemplary operating logic 160 that may be employedby an exemplary controller to operate the modular AC unit in auto mode.In the illustrated embodiment, the auto mode may be set as the defaultoperating mode when the modular AC unit is powered ON. However, itshould be noted that in other embodiments, other modes (e.g., heat mode,cool mode, vent mode) may be activated any time the modular AC unit isON. In the illustrated embodiment, however, the auto mode logic 160begins when the controller checks whether the modular AC unit is ON(block 162). When the modular AC unit is powered ON, auto mode isactivated (block 164), and a time delay may be implemented (block 166).That is, once the unit is powered ON, a delay time period (e.g., 5seconds) allows for operator selection of an alternate mode prior toimplementation of the auto cycle.

As such, the controller checks for a user selected mode (block 168), andif an alternate mode (e.g., cool mode or heat mode) is selected, thecontroller implements the chosen mode (block 170). If the user has notselected a mode during the delay period, the controller proceeds to automode. In particular, the controller inquires as to whether a regionaljet is selected (block 172), and if so, the controller sets the dampersetting to a first set point (block 174), for example, approximately27%. The controller further checks if a narrow body jet is selected(block 176), and if so, the controller sets the damper setting to asecond set point (block 178), for example, approximately 45%. Thecontroller further checks if a wide body or jumbo jet is selected (block180), and if so, the controller sets the damper setting to a third setpoint (block 182), for example, approximately 100%. Once the dampersetting has been set by the controller based on the selected aircraft,auto mode may be implemented to maintain the temperature in the desiredrange, and the controller may continually monitor for a change in mode(block 184).

In this way, the exemplary controllers disclosed herein may be adaptedto increase the flexibility of the illustrated modular AC units ascompared to traditional systems. That is, even the modular AC units ofhigh capacities may be configured to service small aircraft by adjustingthe damper setting accordingly. As such, any selected aircraft may beserviced by any modular AC unit as long as the necessary output capacityof the aircraft does not exceed the maximum operational output of themodular AC unit.

FIG. 11 illustrates control logic 186 that may be implemented for amodular AC system that considers a variety of applicable factors todetermine the startup sequence of the modular unit. The modular AC unitis first powered ON (block 188) and the controller checks the size ofthe modular AC unit (block 192), the aircraft size selected (block 194),and the HVACR mode (block 196). Considering the aircraft type, HVACRmode, and the modular AC unit size, the controller may implement controlin at least one of a heat mode, a cool mode, an auto mode, and a ventmode (block 198). For example, if cool mode has been selected, thecontroller may implement the logic of FIGS. 12 and 13.

The control logic 200 of FIG. 12 for cool mode begins when cool mode isenabled (block 202), for example, by user selection or automaticdetermination by the controller. During cool mode, the controller may beadapted to receive feedback regarding ambient air temperature (block204), aircraft size (block 206), and ambient humidity (block 208) and tocalculate the appropriate number of stages of compressors needed toachieve the desired cooling based on such feedback (block 210). Once thenecessary number of stages of compressors has been calculated, thecontroller activates the appropriate number of compressors (block 212).Subsequently, during operation, the controller may utilize a detecteddischarge air temperature (block 214) to continuously update the numberand location of activated compressors (block 216).

For instance, embodiments of the disclosed controller for the modular ACunit may input detected discharge air temperature into a proportionalintegral derivative (PID) control block to determine how many and whichcompressor stages should be activated to maintain the discharge airtemperature at a predetermined set point (e.g., 24° F.). For furtherexample, if the predetermined set point cannot be reached with theactivated number of compressors, additional compressor stages may beactivated until the desired set point is reached. The controller mayalso be configured to control which compressors are activated anddeactivated. For example, the controller may assign an activationtemperature and a deactivation temperature to each compressor. Eachcompressor may then be activated at the activation temperature anddeactivated at the deactivation temperature.

FIG. 13 illustrates one exemplary method in which the controller maycalculate the number of necessary compressor stages during the coolingmode startup. In this embodiment, the method includes determining themass airflow rate for the given application (block 218), determining aninlet air enthalpy (block 220), determining desired output air enthalpy(block 222), and finally determining the appropriate number of stages ofcompressors needed for the given application based on the previouslydetermined values (block 224). For example, in one embodiment, thenumber of stages of compressors may be calculated according to equation(1):#stages=[a*M _(airflow) ]*[b*(H _(i,air) −H _(o,air))],  (1)where a is an appropriate scaling constant, M_(airflow) is the massairflow rate for the given aircraft model, b is an appropriate scalingconstant, H_(i,air) is the inlet air enthalpy, and H_(o, air) is theoutlet air enthalpy. An appropriate mass airflow rate may be determinedby the controller based on the operator aircraft selection and themodular AC unit size. An appropriate inlet air enthalpy may becalculated by the controller based on temperature and humidity feedbackreceived from sensors located in the modular AC system. The air outputenthalpy may be determined by the controller either via a lookup tableor via direct calculation based on the unit capacity.

FIG. 14 illustrates a method 226 that may be utilized by an exemplarycontroller to control operation of the one or more condenser fans in themodular AC unit. The exemplary method 226 may offer distinct advantagesover traditional control systems which switch the condenser fans ON andOFF as the compressor unit is activated and deactivated. For example,presently disclosed controllers may provide for individual control ofeach of the condenser fans independent of the activation or deactivationof the associated compressor module. As such, the exemplary controllerdisclosed herein may operate more efficiently than previous systems.

Specifically, the method 226 includes detecting a refrigerant dischargepressure (block 228) and determining the necessary number of condenserfans to be activated based on the detected discharge pressure (block230). As such, embodiments of the modular AC units may include pressuretransducers disposed throughout that are adapted to detect therefrigerant discharge pressure. The controller may check whether theambient temperature exceeds a predetermined threshold (e.g., 95° F.,block 232). If the ambient temperature does exceed the threshold, allthe condenser fans in a given module may be activated before thecompressor is activated (block 234), for example, to possiblysubstantially reduce or eliminate the effects of an instantaneous spikeof discharge pressure when the compressor is activated in a hightemperature ambient condition.

The controller may also check to determine if any of the dischargepressure transducers are malfunctioning (block 236), and if so, all thecondenser fans in the module may be activated (block 234) since thepressure feedback is unreliable. The controller continues monitoring therefrigerant discharge pressure and adjusting the number of activatedcondenser fans in each compressor module throughout operation (block238). Again, such a controller may facilitate unit efficiency becausethe condenser fans are only activated as needed. For example, such acontrol method allows for no fans in a compressor module to be activatedif the discharge pressure is below a predetermined threshold.

FIG. 15 illustrates an exemplary method 240 that may be employed by thepresently disclosed controller to control opening and closing of the hotgas valves that are configured to determine the quantity of hot gasbeing circulated to the evaporator coils to substantially reduce orprevent the likelihood of freezing. The method 240 includes determininga suction pressure set point (block 242) and monitoring the actualsuction pressure over a given time interval (block 244) and employingproportional integral derivative (PID) control. The method 240 alsoincludes determining an appropriate valve opening percentage for eachhot gas valve based on a rate of change of suction pressure (block 246).For example, each hot gas valve may be opened anywhere between 0% and100% to achieve the desired suction pressure set point or to maintainthe actual suction pressure within a desired range.

The method 240 may further include steps to allow for the staging of thecompressors to be controlled via the gas valve opening percentages. Forexample, the method includes the step of summing the open percentages ofeach of the hot gas valves to determine a total hot gas opening value(block 248). The method 240 also includes a check to determine if thecalculated total gas opening value exceeds a predetermined threshold(e.g., 125%, block 250). If the threshold is exceeded, the lastoperational downstream compressor is deactivated (block 252), and thetotal hot gas opening value is reset to zero (block 254). If thethreshold is not exceeded, the method 240 includes a step to check foractivation of additional compressors (block 256). When an additionalcompressor is activated, the total hot gas opening value is again resetto zero (block 254). In this way, the controller may optimize coolingcapacity to allow more efficient unit operation as compared totraditional systems.

FIGS. 16 and 17 illustrate methods that may be utilized by thecontroller to alert a user to critical and non-critical system faults,respectively. Specifically, FIG. 16 illustrates a critical faultalerting method 258. The method 258 includes detecting a critical fault(block 260) and activating a flashing fault light to notify the userthat a critical fault has occurred (block 262). After alerting the user,the controller monitors the system for depression of the fault lightpushbutton (block 264). If the fault light pushbutton is not depressed,the fault light continues to flash to alert the user of the error. Ifthe user depresses the fault light pushbutton, the aircraft model lights(e.g., four lights disposed in a row) are activated (block 266). Thecontroller then utilizes such lights to display a binary enumerationindicating the type of critical fault that has occurred (block 268). Forexample, in one embodiment, the user may reference a lookup table ofcodes that indicate the particular error based on the communicatedbinary enumeration. For further example, a code of 0001 may indicate anambient probe failure, a code of 0010 may indicate a duct probe failure,and so forth.

Likewise, FIG. 17 illustrates a non-critical fault alerting method 270.The method 270 includes detecting a non-critical fault (block 272) andactivating a continuously illuminated fault light to notify the userthat a non-critical fault has occurred (block 274). After alerting theuser, the controller monitors the system for depression of the faultlight pushbutton (block 276). If the fault light pushbutton is notdepressed, the fault light remains illuminated to alert the user of theerror. If the user depresses the fault light pushbutton, the modular ACunit mode lights (e.g., four lights disposed in a row) are activated(block 278). The controller then utilizes such lights to display abinary enumeration indicating the type of non-critical fault that hasoccurred (block 280). For example, in one embodiment, the user mayreference a lookup table of codes that indicate the particular errorbased on the communicated binary enumeration. For further example, acode of 0001 may indicate relative humidity sensor failure.

It should be noted that although in the described embodiment, theaircraft model lights are utilized to indicate critical faults and themode lights are utilized to indicate non-critical faults, in otherembodiments, such an arrangement may be reversed. Furthermore, the faultlight may be configured to remain illuminated to indicate a criticalfault and to flash to indicate a non-critical fault. Indeed, any of avariety of suitable ways to communicate a binary error code indicating acritical or non-critical fault to a user utilizing lights or other meanslocated on a control panel of the modular AC unit may be employed.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. A condenser assembly, comprising: a housingdefining an airflow volume; a divider separating the airflow volume intoa first volume and a second volume; a first condenser coil disposed in aside of the housing adjacent to the first volume; a second condensercoil disposed in a side of the housing adjacent to the second volume; afirst fan disposed in a first end of the housing to blow air through thefirst condenser coil and the first volume; and a second fan disposed ina second end opposite the first end of the housing to draw air into thesecond volume and through the second condenser coil.
 2. The condenserassembly of claim 1, further comprising a third fan disposed in thefirst end of the housing adjacent to the first fan.
 3. The condenserassembly of claim 2, further comprising a fourth fan disposed in thesecond end of the housing adjacent to the second fan.
 4. The condenserassembly of claim 3, further comprising control circuitry coupled to thefirst fan, the second fan, the third fan, and the fourth fan andconfigured to independently control the operation of the first fan, thesecond fan, the third fan, and the fourth fan.
 5. The condenser assemblyof claim 4, wherein the control circuitry is configured to independentlycontrol operation of the first fan, the second fan, the third fan, andthe fourth fan based on refrigerant head pressure.
 6. The condenserassembly of claim 1, wherein the divider comprises two plates separatedby an insulating medium.
 7. The condenser assembly of claim 6, whereinthe insulating medium is air.
 8. The condenser assembly of claim 1,wherein a temperature of air in the first volume is lower than atemperature of air in the second volume.
 9. The condenser assembly ofclaim 1, wherein the first condenser coil and the second condenser coilare micro-channel condenser coils.
 10. The condenser assembly of claim1, wherein the housing comprises a grid coupled to the second condensercoil and configured to approximately evenly distribute incoming airacross the length of the second condenser coil.
 11. The condenserassembly of claim 1, wherein the first condenser coil and the secondcondenser coil are parallel.